DISEASES OF COWS. 



439 



supposed section of the udder made lengthwise through 

 it, from front to rear. At a is the milk vein, so-called, 

 but really the abdominal subcutaneous vein, which in 

 some cows has an enormous volume. The capillary or ulti- 

 mate branches of this vein are very numerous, and connect 

 and anastomose, or form a continuous net-work, with the 

 capillary or ultimate branches of the subcutaneous ab- 

 dominal artery which supplies the mammae with blood. 

 These capillaries surround and envelop the gland vesicles, 

 shown at figure 103. These gland vesicles here figured 

 appear as magnified four times. Each one of these mi^ 

 nute vesicles has the office or function of secreting the 

 milk from the blood supplied to it by the arteries, and 



Fiff. 103. 



Fig. 104. 



forming cell tissue, and the blood which has parted 

 with its quota of cell matter and fat then passes to its 

 veins on its way to the lungs and heart for purification 

 and a fresh supply of nutriment from the great thoracic 

 vein which pours into the heart the blood newly formed 

 from the digested food. Thus the milk is as direct a 

 product of the blood as are the muscular tisue and 

 fat, which are deposited in their proper places from the 

 proper vessels of supply. These gland vesicles are clus- 

 tered in groups around the lactiferous or milk-conveying 

 ducts, much as a bunch of grapes is clustered around the 

 stem upon which they hang from the vine-stalk. They 

 are about l-200th of an inch in diameter. Each vesicle 

 contains a number of cells and each cell has a nucleus or 



